1. Field of the Invention
The present invention relates to improvement in or relating to a semiconductor photoelectric conversion device which has a light-transparent substrate, a light-transparent first conductive layer formed on the substrate to serve as an electrode, a non single-crystal semiconductor laminate member formed on the first conductive layer and having formed therein at least one PIN or PN junction, and a second conductive layer formed on the non-single-crystal semiconductor laminate member to serve as an electrode. Also, the invention pertains to a method for the manufacture of such a semiconductor photoelectric conversion device, improvement in a light-transparent substrate for use therein and a method for the manufacture of such a light-transparent substrate.
2. Description of the Prior Art
In conventional semiconductor photoelectric conversion devices of the abovesaid type, the the light-transparent substrate usually has a flat surface with which the light-transparent first conductive layer serving as an electrode is in contact. Consequently, the boundaries between the light-transparent substrate and the light-transparent first conductive layer, between the light-transparent first conductive layer and the non-single-crystal semiconductor laminate member, and between the non-single-crystal semiconductor laminate member and the second conductive layer are flat boundaries extending along the substrate surface.
With the conventional semiconductor photoelectric conversion device of such a structure, light incident on the light-transparent substrate on the side opposite from the first conductive layer mostly enters thereinto through the substate, but a porion of the light is reflected at the boundary between the substrate and the first conductive layer and back to the outside through the substrate.
Further, the light having entered into the light-transparent first conductive layer mostly enters into the non-single-crystal semiconductor laminate member, but a portion of the light is similarly reflected at the boundary between the first conductive layer and the non-single-crystal semiconductor laminate member and back to the outside through the first conductive layer and the light-transparent substrate.
The light having entered into the non-single-crystal semiconductor laminate member travels therein in its thickwise direction, creating electron-hole pairs. When the light travels in the non-single-crystal semiconductor laminate member from the boundary between it and the light-transparent first conductive layer to the boundary between it and the second conductive layer, the light travels only a distance equal to the thickness of the non-single-crystal semiconductor laminate member.
Holes (or Electrons) of the electron-hole pairs generated in the non-single-crystal semiconductor laminate member flow across thereto to reach the light-transparent first conductive layer, and the electrons (or holes) flow across the non-single-crystal semiconductor laminate member to reach the second conductive layer, developing electromotive force across the first and second conductive layers. In this case, a maximum value of the difference between the thickness of the non-single-crystal semiconductor laminate member and the thickness of the non-single-crystal semiconductor layer of the semiconductor laminate member formed in contact with the first conductive layer cannot be selected greater than a maximum distance of travel over which the electrons (or holes) of the electron-hole pairs, created at and in the vicinity of the boundary between the non-single-crystal semiconductor layer of the non-single-crystal semiconductor laminate member formed in contact with the first conductive layer and another non-single-crystal semiconductor layer formed thereon, can flow to reach the second conductive layer. Therefore, when light travels in the non-single-crystal semiconductor laminate member from the boundary between it and the first conductive layer to the boundary between it and the second conductive layer, the light does not travel in excess of the abovesaid maximum distance of travel in the region from the boundary between the non-single-crystal semiconductor layer of the non-single-crystal semiconductor laminate member formed in contact with the first conductive layer and the non-single-crystal semiconductor layer formed thereon to the boundary between the non-single-crystal semiconductor laminate member and the second conductive layer.
For the reason given above, the prior art semiconductor photoelectric conversion deveices are extremely poor in the efficiency of utilization of incident light and large in the actual distance of travel of the carriers (electrons or holes) to the conductive layer serving as the electrode, and hence are very difficult to achieve a photoelectric conversion efficiency higher than 8%.